The present invention relates to a semiconductor sealing epoxy resin composition, and, more particularly, to a semiconductor sealing epoxy resin composition using a flexibilizer comprising a reactant product of denatured silicone oil having an epoxy group and phenolnovolak resin, which exhibits the heat and humidity resistance of epoxy resins, as well providing a hardened material with low elasticity, great strength, and low expansion ratio.
In recent years, semiconductor devices tend to be enlarged and greatly integrated, and if such semiconductor devices are sealed by a conventional epoxy resin composition, the chip can generate cracks or the bonding wire can be cut due to the thermal stress caused between the difference in the linear thermal expansion ratio of the chip (or lead frame) and the sealing resin. The reliability of the semiconductor products therefore deteriorates. The reason for this deterioration the nature of conventional semiconductor sealing epoxy resins; they have been developed for achieving heat resistance and water resistance using a hardened material which is too hard and lacks flexibility, therefore creating great stress in the device.
In order to minimize this stress, the materials which make up the semiconductor device need to have a lower elastic modulus, expansion ratio and glass transition point. However, in order to retain the moisture resistance and head resistance, the glass transition point needs to be sufficiently high. A method of realizing a low stress comprises using a flexibilizer. However, when the conventional flexibilizer is used to lower the elastic modulus, the glass transition point of the hardened material can be excessively lowered, causing the electric characteristics and the moisture resistance of the semiconductor device to deteriorate at high temperatures, thus making it not suitable as a semiconductor sealing resin composition.
In order to improve the semiconductor's electric characteristics at high temperatures, low elastic modulus silicone resin can be used as the flexibilizer and is mixed with an epoxy resin. However, a use of the silicone resin causes deterioration in the adhesiveness between the resin and metal, thus increasing the vapor moisture transmission, leading to an unreliable moisture resistance.
As a flexibilizer exhibiting an excellent moisture resistance without lowering the glass transition point, a denatured rubber epoxy flexibilizer is proposed. This flexibilizer is obtained by reacting polybutadiene having carboxyl groups at both ends thereof, or a copolymer of a polybutadiene having carboxyl groups at both ends thereof, and acrylonitrile with an epoxy resin. However, when such flexibilizer is stored at high temperatures, unsaturated bonds in the polybutadiene structure deteriorate due to oxidation, resulting in the loss of flexibility.
Furthermore, a semiconductor sealing epoxy resin composition exhibiting an excellent heat resistance is disclosed in Japanese Patent Application Laid-Open No. 58-2322 in which phenolnovolak epoxy resin and phenolnovolak resin are mixed into the epoxy resin as the hardening agent. However, this composition suffers from insufficient crack resistance. In Japanese Patent Application Laid-Open No. 58-108220, a semiconductor sealing epoxy resin composition exhibiting excellent heat resistance (glass transition point and so on) and excellent crack resistance is disclosed which contains 0.05 to 10 wt % of a rubber component. However, this composition deteriorates when it is subjected to a high temperature standing test (strength can be lowered and its weight can be also reduced).